1. Technical Field
The present invention relates to telecommunications and, more particularly, to mobile telecommunications terminals and utilization of network services.
2. Discussion of Related Art
Multimode terminals are getting more and more popular. Multimode terminals are capable of operating on different system modes (using different radio access technologies and/or able to attach to different core networks). Examples of different system modes are GERAN, WCDMA, TDMA, AMPS, CDM 2000, WLAN, Bluetooth etc. Multimode networks may support different types of interworking between the system modes supported by the terminal.
Currently the terminal already provides some information about its capability in different system modes, making the network aware which services the terminal can support in different system modes. An example is a GERAN terminal indicating its capabilities; in addition to the capabilities for GERAN access technology, also if it supports WCDMA and/or CDM 2000 radio access technologies. The terminal may have quite different support for services depending on the serving system mode. For example, simultaneous packet and circuit switched service is only possible if both the GERAN network and terminal support dual transfer mode (DTM) while this service is always supported by a GERAN/UTRAN dual mode terminal when served by UTRAN. Similarly, if the GERAN network does not support high speed data, then the circuit switched data rate is limited to 9.6 kbit/s for GERAN access while a higher data rate is likely available through WCDMA and an even higher data rate through WLAN. GERAN again might support a location service when any of the other modes supported by the multimode terminal do not support this service. However, when the terminal requests a service, the request is limited to the services supported by the terminal in the currently serving system mode, additional restrictions may be set if the network indicates non-support for some specific network capabilities.
In 3GPP standardisation, different vendors are proposing different ways to solve specific problems where GERAN capabilities are not enough to support a service and thus inter-system change from GERAN to UTRAN is proposed. For example, 3GPP TSG-SA WG1 #21 (Sophia Antipolis, France Jun. 7-11, 2003) proposes to allow a UE that has CS multimedia capability and that is camping on a GERAN cell but is also within UTRAN coverage to setup a CS multimedia service using a UDI 64 kbit/s bearer in UTRAN. Another example is 3GPP TSG-SA2 #33 (also Jun. 7-11, 2003) which introduces a proposal for a new procedure for dual CN connection where a UMTS/GSM terminal roaming in GSM in the neighbourhood of UTRAN coverage is allowed to request a dual CN connection to the BSS, even if the MS is not Class A or if DTM is not supported by the MS and/or the BSS, in order to indicate that a handover or a cell change order to UTRAN should be favoured by the BSS.
Currently there already exist other similar problem cases for other services as well, and the above mentioned proposed solutions by different vendors are not applicable for solving the problems for these other cases but are only directed to narrow and particular problems. The difficulty in these solutions is that they are targeted to a specific problem and are not suitable for solving the issue in generic way (though, these proposals are not actually acceptable to solve the mentioned problems). In this invention disclosure it is shown that a generic mechanism should be applied into the 3GPP specifications to solve the problem in a generic way.
A further example solution is given in the EPO patent No 0716797B1 where the mobile station utilises service specific PLMN preference lists and where the mobile station then selects the PLMN according to the corresponding preference list for the service requested by the user.
Still another example is given in the Finnish patent FI 105309B where the mobile station is aware of the different services supported by different available PLMNs and where the mobile stations selects the PLMN according to the requested service.
Still another example is given in the US patent application 2003/0114158A1 where terminal either directly or indirectly requests intersystem handover in order to establish the requested service. In this patent the preference list in either terminal or network is needed in order to tie the specific service to the specific system.
The disadvantage of these solutions is that the mobile station awareness of the services available from different PLMNs cannot be easily arranged. Also the support of services by different PLMNs may not only depend on the capabilities of the PLMN but also e.g. on the load of the networks and then the support of a specific service may be time dependent. Also the service availability may be location dependent e.g. as a function of the capabilities of the serving cell. Also the disadvantage is the need to have service/content based preference lists either in terminal or in network. Furthermore the optimum PLMN cannot be selected for mobile terminated services in which case the mobile station would not be aware of the service in advance and then cannot select the appropriate PLMN in advance and the service request would be rejected already by the PLMN where the mobile station is attached at the time of the service establishment attempt. Hence the prior art does not provide a solution for a fully flexible service request in respect to the terminal and the network capabilities in different modes.